This invention relates to a coil device utilized for various types of electronic apparatuses such as a display unit, power supply equipment and the like.
FIG. 3 is an illustration showing an example of known process steps for assembling a known toroidal type coil device. The coil device generally denoted by reference numeral 20 comprises a coil body with a wiring coil wound therearound, which coil body is composed of a synthetic resin core cover 30 with a core 22 received therein, and a synthetic resin base 24 which is provided with terminals 25 and on which the coil body is to be mounted.
The coil device 20 is assembled in the following sequential steps, for example.
First, toroidal magentic core 22 is received between case halves 21, 21 and integrally assembled into a unitary structure with the core cover 30. The core cover 30 thus obtained is then placed on the base 24 and a claw-like portion 23 formed on its bottom portion is brought into engagement with an edge portion of an engagement hole 26 formed in a central portion of the base 24. At that time, in order to eliminate attachment chattering (looseness of joints) of the core cover 30, the core cover 30 and the base 24 are attached together by adhesive agent or the like after the claw-like portion 23 is engaged with the engagement hole 26. After the core cover 30 and the base 24 are firmly attached together, a terminal portion of the wiring coil is soldered to a pin terminal 25 projecting from the base 24. By doing so, the procedure for assembling the coil device 20 is completed. The winding operation of the wiring coil 27 is performed after the core cover 30 is assembled or after the core cover 30 is firmly attached to the base 24.
However, the engagement mechanism between the core cover 30 and the base 24 has such a shortcoming that the engagement portion (namely, the claw structure) is inevitably reduced in size compared with the core cover 30 in view of structure, with the result that the assembled coil device 20 is inferior in vibration resistance and shock resistance. For this reason, it is difficult to apply the above engagement mechanism to a larger-sized core without sacrificing reliability. If adhesive agent or the like is used in order to enhance vibration resistance and shock resistance, the assembling process steps and material expenses are increased, thus resulting in higher manufacturing cost.